They were arrested hours after the attack in the hotel where they were staying in the city.

Lawyers for the three said they had come to Cardiff on October 4 last year for a “pleasant night out” and not to cause trouble.

They appealed for prison sentences imposed to be suspended, saying they needed their freedom to complete the last few months of their apprenticeships, but Recorder Wyn Rees refused.

Solicitor Stuart, for Bowen, said: “The incident unfolded in front of him and he joined in.”

The judge agreed nothing would have happened if Mahoney had not started the trouble but told the court: “I would be failing in my public duty if there were not immediate custodial sentences.

“This has been a terrible case to listen to – the description given by an independent witness who knew none of them was quite horrific.

“All three were punching and kicking while he lay defenceless on the floor. There was blood everywhere.

“None of them expected to cause such serious damage but when you repeatedly kick and punch someone, nasty and serious injuries are likely to follow.”

All three defendants had previous convictions for public order breaches and Evans and Bowen had been in court for assault in the past.

Mr LLoyd said: “At first they denied it but pleaded guilty before trial.

“Mr Morris was in the bar with his girlfriend and her friend and when there was a suggestion of flirting going on, words were exchanged.

“Without warning Christian Mahoney punched him and he was down.

“He can remember little of what happened next but witnesses recall his girlfriend being hysterical as he was attacked and they were said to be taking it in turns to assault him, kicking him to his ribs, head and face.